The present invention relates to a safety coupling for pressurised conduits, wherein the safety coupling includes a coupling plug and a coupling housing.
From EP-B-0,598,077 there is known a plug-in safety coupling. With the known safety coupling a pressurised conduit introduction bore is incorporated in the coupling housing and a blocking element with a sealing bore is sealingly mounted therein. A coupling plug may be sealingly introduced into the blocking element and thanks to a slot guide which is present the coupling plug with the blocking element may be pivoted from a blocking position into a conducting position. In the conducting position the pressurised conduit introduction bore is flush with a through bore in the blocking element in which the coupling plug is introduced. The coupling plug comprises a retaining shoulder which on pivoting from the introduction position into the conducting position of the safety coupling comes to bear on the inner side of the coupling housing. In the conducting position thus the bearing pressure of the pressurised medium presses the coupling plug on the inner side onto the coupling housing. The then occurring static friction is directly proportional to the occurring pressure. The known coupling according to the mentioned document EP-B-0,598,077 is usually suitable for pressurised conduits such as are common in workshops, with which there prevails a pressure of a few bar. In this field the known plug-in safety coupling has proven its worth on many occasions. The mentioned safety coupling also represents a suitable solution for smaller dimensions, such as those which are used with pneumatic controls.
A further development of the above mentioned solution is known from EP-B-0,632,872. In this solution there is additionally provided a spring-biased locking means which additionally locks the pivotable blocking element in particular in the conducting position, in order to prevent a decoupling if the two conduit ends to be connected to one another are moved such that under certain circumstances a de-securement would undesirably take place.
With insertable safety couplings for pressurised conduits for transmitting higher pressures one often uses sleeve-like connections which must be mutually screwed. Such connections then however often have no blocking element and may only be coupled in the unloaded condition. Indeed in the building trade one often applies compressors by way of which relatively high pressures are produced. The corresponding pressurised flexible tubings have a relatively large diameter. Accordingly the pressures occurring at the couplings are high. Because the couplings are often subjected to heavy contamination, and in many cases loadings occur due to outside effects, accordingly suitable couplings need to be relatively simple, correspond to high safety demands and must be able to be manufactured inexpensively. It is indeed in the building trade that one often works under the pressure of time. Accordingly it would be advantageous to offer a safety coupling with which the corresponding pressurised flexible tubings may be coupled and decoupled also under the occurring operating pressure. At the same time one must ensure that in the region of the coupling the pressure on decoupling is completely reduced so that a residual pressure does not shoot away the decoupled end of the flexible tubing.
Per se the known previously described solutions with regard to safety technology as well as with regard to the design simplicity and inexpensive manufacture would be suitable in order also to be able to be applied in the building trade. However it has been shown that the occurring pressures are so high that a decoupling is only possible at all with a large force effort. The friction forces between the coupling plug and the coupling housing under the occurring pressure forces are so great that only extremely strong operating persons may decouple such a coupling.